1. Field of the Invention
The present invention relates to a tangential grinding resistance measuring method and apparatus for a grinding wheel in which a grinding wheel layer having abrasive grains bonded with a bond material is formed on a grinding surface. It also relates to a grinding condition decision method and apparatus and a wheel life judgment method and apparatus for such a grinding wheel which are practiced by utilizing the tangential grinding resistance measuring method and apparatus.
2. Discussion of the Related Art
Heretofore, for deciding a grinding condition for a grinding wheel in which a grinding wheel layer having abrasive grains bonded with a bond material is formed on an outer circumferential surface of a disc-like core member, there has been implemented a method in which a worker evaluates grinding burns on a workpiece after actual grinding of the same and sets another grinding condition again if a predetermined standard is not satisfied. However, this grinding condition decision method relies on try and error in setting a grinding condition and hence, requires a long time. It also relies on worker's experiences in setting the grinding condition and is liable to make the grinding condition fluctuate or vary in dependence on workers.
On the other hand, there has been proposed a grinding condition decision method described in Japanese unexamined, published patent application No. 4-315571. This grinding condition decision method will be described hereafter. First of all, tolerances for at least one of a normal grinding resistance and a tangential grinding resistance as well as for the ratio therebetween are set in advance. A normal grinding resistance and a tangential grinding resistance are measured during a grinding operation, and a ratio therebetween is calculated. Then, where the ratio is within the tolerance, the tolerance and the measured value of at least one of the normal grinding resistance and the tangential grinding resistance are compared to decide a grinding condition.
However, in the grinding condition decision method described in the aforementioned Japanese application, the relation between the tolerances and the grinding burn is indefinite, and it is hard to say that the evaluation of the grinding burn is satisfactory.
Heretofore, there has been known a wheel life judgment apparatus described in Japanese unexamined, published patent application No. 11-10535. The wheel life judgment apparatus is of the character that a wheel life is judged by measuring ultrasonic waves of an extremely high frequency (i.e., acoustic emissions) which are emitted when abrasive grains are crushed. According to the wheel life judgment apparatus, the wheel life can be judged based on the correlation which seems to exist between the crush of the abrasive grains and the magnitude of the acoustic emissions.
Further, there has also been known another wheel life judgment apparatus described in Japanese unexamined, published patent application No. 2003-25223. The wheel life judgment apparatus is of the character that a wheel life is detected by measuring an irregularity (an undulation on a grinding surface) which is formed by a part of the abrasive grain surface with pores having been stuffed and another part thereof with pores not having been stuffed. According to the wheel life judgment apparatus, the wheel life can be judged based on the correlation which seems to exist between the crush of the abrasive grains and the dimension of the undulation on the grinding surface.
However, the wheel life judgment apparatus described in the last mentioned two Japanese applications are to make a judgment in dependence on the magnitude of the acoustic emissions or the dimension of the undulation on the grinding surface, but are not to make a judgment based on a tangential grinding resistance which is directly concerned with the wheel life. Therefore, in the wheel life judgment apparatus, the wheel life cannot necessarily be judged precisely.